Rotary distributors



United States Patent ROTARY DISTRIBUTORS Angelo Montani, Baltimore, Md.,assignor of one-half to Communication Measurements Laboratory, New York,N. Y., a partnership Application May 15, 1952, Serial No. 287,993

3 Claims. (Cl. 333-7) This invention relates to rotary distributors ofthe type used in multiplex signalling apparatus.

A rotary distributor may be used, for example, to obtain, in an outputchannel, a signal which is a series of samples of signals present in aplurality of input channels.

A widely used rotary distributor is a segmental contact device in whicha rotary contact or brush passes successively over a plurality ofstationary contacts. Distributors of the rotary contact type have someinherent drawbacks which have been a cause of considerable trouble.

' One of these drawbacks is the unavoidable chatter of the contacts.Another drawback is the wear of the contacts. A third drawback is alimitation on the speed of the rotary distributor, as both chatter andwear increase with speed. A fourth drawback is the possible deposit, atthe contacts, of metallic particles which may bridge two segments andintroduce objectionable crosstalk.

It is an object of the present invention to provide a signal distributorwhich avoids using segmental contact devices.

It is another object of the present invention to eliminate transienteffects due to chatter in high speed rotary distributors.

It is a further object of the present invention to eliminate the effectsof contact wear in rotary distributors.

According to the present invention, these drawbacks are eliminatedthrough the use of a rotary distributor in which signal coupling iseffected capacitively, the segmental contacts having been eliminated.

Other and incidental objects of the present invention will be apparentfrom a reading of the following specification and an inspection of theaccompanying drawings in which:

Figure 1 is a cross-sectional view of one embodiment of the presentinvention, and

Figure 2 is an exploded view of another embodiment of the presentinvention.

Referring to Figure 1, there is shown a surface of conductive material5. This surface 5 is mechanically and electrically connected to a hollowcylinder 7 by means of arm 9. A cylinder 11 is concentrically locatedinside cylinder 7, the common center being designated as 12. Bothcylinders 7 and 11 are made of conductive material, and are separated byan air gap 13. Cylinder 7 is mounted so as to rotate about cylinder 11,which is stationary.

A lead 15 electrically connects cylinder 11 to a terminal of a resistor17, the other terminal of which is grounded. The terminals of resistor17 are the input terminals of utilization circuit 19.

Eight surfaces 21 through 28, made of conductive material, are arrangedaround a circumference which is concentric with cylinders 7 and 11, andhas a radius 29. Radius 29 is larger than the radius between center 12and surface 5, the difference between these radii forming an air gap 31.The surfaces 21 through 28 are mechanically mounted on an insulatingmember 33 by means of stems such as 35. Surfaces 21 through 28 areelectrically connected to input channels 41 through 48 respectively.

Eight surfaces 51 through 58, made of conductive material, are arrangedaround a circumference having its center at 12, and having a radius 59.Radius 59 is slightly greater than radius 29. Surfaces 51 through 59 aremechanically mounted on insulating member 33 by means of Stems such as(it). Surfaces 51 through 59 are electrically grounded by means ofcommon ground connection 61.

The surfaces 21 through 28 may be called input plates, while thesurfaces 51 through 58 may be called ground plates. Surface 5 may becalled an output plate. It can be seen that input plates and groundplates are so disposed that, as the output plate 5 rotates around center12, the output plate 5 alternately faces an input plate and a groundplate.

The input plates 21 through 28, and the ground plates 51 through 5%, arein spaced relationship from each other, so that there is no electricalcontact between a ground plate and an input plate. The ground plates areshown to be wider than the input plates; they are also shown to beprovided with ridges such as 63 and 65. These ridges may extend to thecircumference of radius 29.

The operation of the distributor shown in Figure 1 is as follows.derived from input channels 41 through 48 are applied to the inputplates 21 through 2%. A synchronous motor (not shown) makes output plate5, arm 9 and hollow cylinder 7 rotate about stationary cylinder 11 andcenter rated by air gap 13, also form a coupling condenser, so I thatthe signal present on plate 24 is capacitively coupled to resistor 17and to the utilization circuit 19.

When output plate 5 faces one of the grounded plates, such as 54, theoutput plate 5 is momentarily grounded. This grounding is due to thecapacitive coupling between the output plate 5 and the grounded plate,there being no physical contact therebetween. This grounding avoidscrosstalk between input channels due to the carrying over ofelectrostatic charges from one channel to another. This momentarygrounding of plate 5 by means of the grounded plates is helped by thefact that the maximum (or fully meshed) capacity between the outputplate 5 and any of the grounded plates 51 through 58, is considerablysmaller than the maximum (or fully meshed) capacity between the outputplate and any of the input plates 21 through 28.

The ridges 63 and 65 reduce considerably the capacity coupling betweentwo consecutive input plates, and help in eliminating crosstalk.

The geometry of the whole arrangement is such that an observer, placedinside the circumference of radius 29, cannot see the insulating member33. Thus any erratic electrostatic charge on insulating member 33 willnot influence the potential on output plate 5.

If an alternating potential is applied to one of the input plates 21 to28, the frequency of that potential should be such that the duration ofone cycle is considerably shorter than the time the output plate 5 andthe input plate are etfectively coupled.

If a unidirectional potential is applied to one of the input plates, thecorresponding output potential will be a bipolar pulse having a positiveand a negative amplitude proportional to the unidirectional potential onthe input plate.

In both cases, the potential across resistor 17 comprises a series ofsamples, each sample being proportional to its corresponding inputpotential.

Patented Sept. 4, 1956 Alternating or unidirectional potentials,

Referring to Figure 2, there is shown a surface 69 of conductivematerial. Located within windows of surface 69 are shown six inputsurfaces or plates 71 through 76. These input plates 71 through 76 aremade of conductive material and are electrically connected to inputchannels 81 through 86 respectively. The input plates 71 through 76 areelectrically insulated from surface 69, and surface 69 is grounded.

Facing the input plates 71 through 76 are the output surfaces or plates91 through 96. These output plates are made of conductive material, andare electrically connected together by means of lead 101. Lead 101 isconnected to one terminal of a resistor 103, the other terminal of whichis grounded. The output plates 91 through 96 may be mechanicallysupported by a surface (not shown) similar to surface 69 supporting theinput plates 71 through 7 6.

Between the input and output plates which are stationary, there islocated a rotating plate 105. Plate 105 may be rotated by means of asynchronous motor (not shown). Plate 105 is made of conductive material.Eccentrically located within .it is a window 107. In this window 107there may be air or any other dielectric material.

It will be noted that the input plates 71 through 76, the output plates91 through 96, and the window 107 are located around threecircumferences having radii of the same length, and whose centers are onan axis perpendicular to these radii.

As plate 105 revolves, the window 107 couples capacitively and insuccession each of the input plates 71 through 78 to each of thecorresponding output plates 91 through 98. The potential across resistor103 comprises a series of samples, each sample being proportional to itscorresponding input potential.

It will be noted that Figure 2 .is an exploded view. In practice, thedistances 109 and 111 amount to only a few thousandths of an inch.

Crosstalk between the input plates 71 through 76 is avoided by groundingplate 69 as shown. The rotating plate 105 and plate 69 forming acondenser to ground, plate 105 is also grounded for alternatingpotentials.

It is seen that the previously mentioned drawbacks of segmental contactsare avoided in the rotary distributors constructed in accordance withthe present invention.

What is claimed is:

l. A rotary signal distributor comprising: a first set of fixedconductive members defining surfaces mounted on the circumference of acircle perpendicular to and centered on an axis, the members of saidfirst set being electrically connected to a common point of referencepotential, a second set of fixed conductive members defining surfacesinsulatively supported and mounted on the circumference of a circleperpendicular to and centered on said axis, the surfaces of said secondset being interposed between the surfaces of said first set, anotherconductive member defining a surface parallel to said axis, and meansfor rotating the surface of said other member about said axis and intospaced parallel relationship successively with each of said fixedsurfaces to form a capacitor therewith, the maximum capacitance betweenthe surface of said other member and a surface of the first set beingsmaller than the maximum capacitance between the surface of said othermember and a surface of the second set.

2. A rotary signal distributor according to claim 1 wherein thecircumference on which the surfaces of said first set are mounted has aslightly larger radius than that of the circumference on which thesurfaces of said second set are mounted.

3. A rotary signal distributor according to claim 2 wherein the surfacesof said first set are provided, near the edges close to the surfaces ofsaid second set, with ridges substantially perpendicular to thesurfaces.

References Cited in the file of this patent UNITED STATES PATENTS1,913,512 Reynolds June 13, 1933 2,402,603 Clark June 25, 1946 2,432,089Carter et al. Dec. 9, 1947 2,477,635 Marchand Aug. 2, 1949 2,679,551Newby May 25, 1954

